I bought it for use with iPod Nano 7. The frequencies range from 87.6 to 107.9 but the device which can indicate how often seems the most appropriate, always advise (almost) 107.9 whatever the where I am in France ...
My old 2004 iTrip connected to an old iPod Mini has frequencies from 87.5 to 108.0 and is less susceptible to interference.